Bass improved through JL Audio 300/2v2, but still problems!

jonywalker · 05-26-2008, 06:19 AM

I just finished my second step of the sound system upgrading with JL 300/2. The first step was the replacement of all OEM speakers, and the most improvement was achieved by that. The new subs were of 4 ohm so I had to add an additional amp to power them. My first try was using a hi-low adatper taping on the sub-output of the OEM amp, I didn't like this way but I had no other choice because I bought a wrong amp with non-balanced input. The result was bad, the bass had very low quality, not well controlled and damped, just lauder. With helps hier in the forum I found correct amps that can accept the BMW HU directly. I chose the JL because of its very promising factory data. The installation was quite simple I just taped the signal from front channels of the HU, chose the sensitivity of high (JL has 0,2mv - 2v and 0,8 mv - 8 v seletable, and turned it at about middle position) and results are much better than I had before, the bass is now very forceful, deeper and well controlled. The 24 dB crossover is fine, it makes big difference to 12 dB to my setting for LP at 130 hz. BUT the sound seems to be little strange, It generated somehow unnormal pressure in my ear as if the speekers were (+-) disordered, but I checked all my wiring (input and output) again and again, nothing is wrong. If I change the poles it sounds little better. I don't have ideal

!
Another phenomenon is: inside is great but if I stand outside the closed car, the whole car seems to crack every where, terrible. But this is constructional weakness of under-seat subsystems.
Does any one know what I did wrong this time again?

jonywalker

jonywalker · 05-26-2008, 06:26 AM

or there is a phase shift for about 180 degree with filter of 4th order, therefor I have to exchange the polarity?

VP Electricity · 05-26-2008, 12:18 PM

The phase MIGHT be the issue. It's usually easy to swap polarity and so we shouldalways try it both ways - sometimes it helps, sometimes it doesn't. You already tried that...

I forget from your previous posts, my apologies - in your car, the HU drives the F and R speakers, right? And what about the subs? What drives the subs? Regardless, your amp should be driven either A), off of the speaker channels that drive the underseat speakers, whether those speakers are HU driven or amp driven - or B), off of the Full-range low-level small-gauge-ire preamp signals from the HU to the amp.

The F speaker outputs to the F door speakers should have all the lowest bass filtered out and are a bad choice for the sub signal. The F preamp outputs from the HU to the amp should not have that problem - that signal should be full range - but in that case the input sensitivity should be set to low, not high, shouldn't it?

Have you tried lowering your LP to around 90 Hz? That's my first idea for sound quality - maybe even lower. I would probably use around 70 myself.

jonywalker · 05-26-2008, 02:06 PM

Hi VP Electricity,
my JL amp is driven off of "B" as you mentioned, with full range low level signal from HU. My previous solution was "A", and hi-low adapter was needed, that was bad since the signal was preprocessed by the factory amp. The factory amp is still there and drives F and R channels, just the sub-channels haven been taken over by the JL amp. Maybe I should apply some loads to the sub-channel output of the factory amp, I am not sure whether or not the open circuit does harm to the transistors. I will keep trying adjusting the crossover point. It is better to use a spectrum meter but I don't have it. My first test result is: 130 hz better than 200 hz, the sound is cleaner. Do you know the OEM crossover point?
BTW. I contacted the JL technical support for whether the JL has the real balanced or quasi-balanced input but still no answer yet. I measured the impedance between both poles of the RCA jack to ground, they are symmetrical.

best regards

VP Electricity · 05-26-2008, 02:36 PM

OK, cool, here are my thoughts:

1) I would try reconnecting the OEM woofers off of the OEM amp. This does fill in the midbass quite a bit. The front 100mm mids can't play low enough to meet any trunk-mounted sub. I have tried this with no ill effects.

2) OEM xover point I believe is about 100 or so, but the differing locations play a large role.

3) I would suggest the very scientific approach of turning the xover knob until it sounds best and THEN looking at what the setting reads. Determine the right setting empirically. The xover settings on amps are notoriously inaccurate and there isn't a lot of precision feel to the knob anyway, so I would experiement and see what you like. I suspect lower than you have it now is best.

BTW, quasi-balanced is the right answer

but you will only get it if you talk to an engineer, I suspect.

jonywalker · 05-26-2008, 07:46 PM

I see, I need to add trunk sub for playing real lower frequences driven by the JL 300/2 if I didn't missunderstand you. However, my OEM woofers have also been replaced with ones semilar to the earthquake SWS-8 like the most people hier did. I read someone replaced his OEM amp with alpine PDX-5, and reported he didn't have sufficient low frequences at the first moment, but it made a big difference as he added an equalizer to it. That is I would prefer to do as I need space in the trunk for other activities, e.g. ski, boots bikes etc...
To accomplish that I need a suitable small and compact 4-channel amp if I decide to replace the OEM amp and add an equalizer doing the fine tuning. May be I would do in quite unscientific way to add a class D amp to the existing class AB system

.

best regards

jonywalker · 05-30-2008, 09:13 PM

what a great sound after I fixed the problem, it was the fault of JL audio, they did the wrong polarity of speaker output so I have to exchange the polarity of just one channel. This was the reason why I got the unusual sond presure that made me crazy, unbelievable! However the sound of 300/2v2 is really great. The previous wiring resulted in 180 degree phase difference between right and left channel, so the most energy was eliminated. I felt the seat trembled but without too much sound and my ears suffered

. My new experienced best setting is: 12 dB xover at 95 Hz, thus introduced a enhanced subsonic automatically without an equalizer at this moment. The bass goes very deep, clean and very quick responsed. I feel so happy to have the JL even they did the small stupid mistake.

05-26-2008, 06:19 AM	#1
jonywalker Private First Class 10 Rep 105 Posts Drives: BMW E91 325d Join Date: Oct 2007 Location: Munich iTrader: (0)	Bass improved through JL Audio 300/2v2, but still problems! I just finished my second step of the sound system upgrading with JL 300/2. The first step was the replacement of all OEM speakers, and the most improvement was achieved by that. The new subs were of 4 ohm so I had to add an additional amp to power them. My first try was using a hi-low adatper taping on the sub-output of the OEM amp, I didn't like this way but I had no other choice because I bought a wrong amp with non-balanced input. The result was bad, the bass had very low quality, not well controlled and damped, just lauder. With helps hier in the forum I found correct amps that can accept the BMW HU directly. I chose the JL because of its very promising factory data. The installation was quite simple I just taped the signal from front channels of the HU, chose the sensitivity of high (JL has 0,2mv - 2v and 0,8 mv - 8 v seletable, and turned it at about middle position) and results are much better than I had before, the bass is now very forceful, deeper and well controlled. The 24 dB crossover is fine, it makes big difference to 12 dB to my setting for LP at 130 hz. BUT the sound seems to be little strange, It generated somehow unnormal pressure in my ear as if the speekers were (+-) disordered, but I checked all my wiring (input and output) again and again, nothing is wrong. If I change the poles it sounds little better. I don't have ideal ! Another phenomenon is: inside is great but if I stand outside the closed car, the whole car seems to crack every where, terrible. But this is constructional weakness of under-seat subsystems. Does any one know what I did wrong this time again? jonywalker
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05-26-2008, 06:26 AM	#2
jonywalker Private First Class 10 Rep 105 Posts Drives: BMW E91 325d Join Date: Oct 2007 Location: Munich iTrader: (0)	or there is a phase shift for about 180 degree with filter of 4th order, therefor I have to exchange the polarity? Last edited by jonywalker; 05-26-2008 at 10:56 AM..
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05-26-2008, 12:18 PM	#3
VP Electricity Brigadier General 301 Rep 3,201 Posts Drives: F34 xDrive Join Date: Jan 2008 Location: portland oregon iTrader: (3)	The phase MIGHT be the issue. It's usually easy to swap polarity and so we shouldalways try it both ways - sometimes it helps, sometimes it doesn't. You already tried that... I forget from your previous posts, my apologies - in your car, the HU drives the F and R speakers, right? And what about the subs? What drives the subs? Regardless, your amp should be driven either A), off of the speaker channels that drive the underseat speakers, whether those speakers are HU driven or amp driven - or B), off of the Full-range low-level small-gauge-ire preamp signals from the HU to the amp. The F speaker outputs to the F door speakers should have all the lowest bass filtered out and are a bad choice for the sub signal. The F preamp outputs from the HU to the amp should not have that problem - that signal should be full range - but in that case the input sensitivity should be set to low, not high, shouldn't it? Have you tried lowering your LP to around 90 Hz? That's my first idea for sound quality - maybe even lower. I would probably use around 70 myself.
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05-26-2008, 02:06 PM	#4
jonywalker Private First Class 10 Rep 105 Posts Drives: BMW E91 325d Join Date: Oct 2007 Location: Munich iTrader: (0)	Hi VP Electricity, my JL amp is driven off of "B" as you mentioned, with full range low level signal from HU. My previous solution was "A", and hi-low adapter was needed, that was bad since the signal was preprocessed by the factory amp. The factory amp is still there and drives F and R channels, just the sub-channels haven been taken over by the JL amp. Maybe I should apply some loads to the sub-channel output of the factory amp, I am not sure whether or not the open circuit does harm to the transistors. I will keep trying adjusting the crossover point. It is better to use a spectrum meter but I don't have it. My first test result is: 130 hz better than 200 hz, the sound is cleaner. Do you know the OEM crossover point? BTW. I contacted the JL technical support for whether the JL has the real balanced or quasi-balanced input but still no answer yet. I measured the impedance between both poles of the RCA jack to ground, they are symmetrical. best regards
	Appreciate 0 Quote

05-26-2008, 02:36 PM	#5
VP Electricity Brigadier General 301 Rep 3,201 Posts Drives: F34 xDrive Join Date: Jan 2008 Location: portland oregon iTrader: (3)	OK, cool, here are my thoughts: 1) I would try reconnecting the OEM woofers off of the OEM amp. This does fill in the midbass quite a bit. The front 100mm mids can't play low enough to meet any trunk-mounted sub. I have tried this with no ill effects. 2) OEM xover point I believe is about 100 or so, but the differing locations play a large role. 3) I would suggest the very scientific approach of turning the xover knob until it sounds best and THEN looking at what the setting reads. Determine the right setting empirically. The xover settings on amps are notoriously inaccurate and there isn't a lot of precision feel to the knob anyway, so I would experiement and see what you like. I suspect lower than you have it now is best. BTW, quasi-balanced is the right answer but you will only get it if you talk to an engineer, I suspect.
	Appreciate 0 Quote

05-26-2008, 07:46 PM	#6
jonywalker Private First Class 10 Rep 105 Posts Drives: BMW E91 325d Join Date: Oct 2007 Location: Munich iTrader: (0)	I see, I need to add trunk sub for playing real lower frequences driven by the JL 300/2 if I didn't missunderstand you. However, my OEM woofers have also been replaced with ones semilar to the earthquake SWS-8 like the most people hier did. I read someone replaced his OEM amp with alpine PDX-5, and reported he didn't have sufficient low frequences at the first moment, but it made a big difference as he added an equalizer to it. That is I would prefer to do as I need space in the trunk for other activities, e.g. ski, boots bikes etc... To accomplish that I need a suitable small and compact 4-channel amp if I decide to replace the OEM amp and add an equalizer doing the fine tuning. May be I would do in quite unscientific way to add a class D amp to the existing class AB system . best regards
	Appreciate 0 Quote

05-30-2008, 09:13 PM	#7
jonywalker Private First Class 10 Rep 105 Posts Drives: BMW E91 325d Join Date: Oct 2007 Location: Munich iTrader: (0)	I fixed the problem what a great sound after I fixed the problem, it was the fault of JL audio, they did the wrong polarity of speaker output so I have to exchange the polarity of just one channel. This was the reason why I got the unusual sond presure that made me crazy, unbelievable! However the sound of 300/2v2 is really great. The previous wiring resulted in 180 degree phase difference between right and left channel, so the most energy was eliminated. I felt the seat trembled but without too much sound and my ears suffered. My new experienced best setting is: 12 dB xover at 95 Hz, thus introduced a enhanced subsonic automatically without an equalizer at this moment. The bass goes very deep, clean and very quick responsed. I feel so happy to have the JL even they did the small stupid mistake.
	Appreciate 0 Quote